1. Field of the Invention
The present invention relates to a method of coating elastomeric components for medicinal purposes.
2. Prior Art
Elastomeric components for applications, in which the pharmacological compatibility of the elastomeric components is an issue, are known in many different forms, especially as closure means for containers for food and pharmacological containers, such as injection stoppers, infusion stoppers or bottle stoppers for spraying devices. DIN ISO 11040, Part 2, requires stoppers for dental capsules made from elastomeric materials that deliver no substances that would have a deleterious effect on the therapeutic action of the injected preparation.
The specifications for rubber parts, i.e. parts which are made from an elastomeric material, in medical areas, which come into contact with aqueous solutions or suspensions during their preparation, storage and use, are generally established by the standards set forth in DIN 58 367, Part 1.
The requirements for elastomeric components or parts in similar applications are similar.
The above-described specifications can be fulfilled as much as possible by the selection of a suitable elastomeric material. Compromises must however be made to fulfill requirements for mechanical properties which is disadvantageous in many cases.
It is also known to provide the elastomeric components with an outer coating that provides the required inertness so that the other required properties of the coated elastomeric parts can be more freely selected.
Each elastomeric component is coated individually in the known methods.
A sanitary article made from rubber, especially a stopper, whose surface is laminated with a plastic film, which comprises a cyclic olefin copolymer (COC), is described in European Patent Document EP 0 497 567 B1.
European Patent Document EP 0 296 878 B1 describes a sanitary rubber object whose surface is provided with a layer of modified polysiloxane cross-linked by irradiation. This layer is applied to the object from a liquid phase.
It is comparatively expensive however to coat individual elastomeric parts. International Patent Document WO 96/349 26 describes a plasma coating process for cumulative coating of elastomeric parts, which are placed in a coating drum in which the elastomeric parts are moved. However this process guarantees no definitely uniform or complete coating on the individual elastomeric parts, since shadow or rubbing effects occur. Thus a considerable over-dimensioning of the layer must take place on average to obtain a predetermined minimum thickness of the coating on all of the parts.
Another method for cumulative coating of elastomeric components is described in U.S. Pat. No. 5,064,083. In this method the elastomeric components are placed individually in recesses or receptacles formed in a grid-like arrangement in a plate coated in certain sections with polyparaxylene. No specific results of this method are however described in this patent.
This method also is very expensive because of the individual treatment required for the individual elastomeric components, which also must be exactly aligned in the receptacles so that only the desired section will be coated.